Original Medicare is made up of two parts: Medicare Part A and Medicare Part B.
Medicare Part A is a portion of Original Medicare that is often times referred to as "Hospital Insurance".
Medicare Part B is the portion of Original Medicare that is often times referred to as "Medical Insurance".
Medicare Part D is for prescription drug coverage. You can enroll separately or combine it with Original Medicare (Part A and Part B).
Medicare Supplement insurance (also known as Medigap) is helps supplement some of the healthcare costs not covered by Original Medicare (Part A and B).
Medicare Part C, or Medicare Advantage, combines Medicare Part A and Part B, and most plans include Part D that may offer extra benefits not covered by Original Medicare.